This invention relates to an endless type tape cassette, wherein an endless tape serving as a recording medium is lodged in a meandering fashion in a cassette, and the tape pulled out of the cassette is again drawn into the cassette by means of a tape drawing reel.
Where recorded video signals for a comparatively short length are repeatedly reproduced by means of a magnetic recording and reproducing device, such as a video tape recorder, an endless tape cassette is generally used.
A conventional tape cassette of the type has been such that an endless magnetic tape is contained in a meandering fashion in a tape housing provided in a cassette body; the endless magnetic tape is successively drawn out of the cassette body, for reproduction; and the magnetic tape is pressed, by means of a press member, against the flank portion of a tape drawing reel, to which is wound a friction member made of rubber, to thereby be drawn into the cassette body. More in detail, the magnetic tape is pulled out of the tape housing to the exterior, via a tape discharge gate provided by cutting part of the partition wall of the tape housing, a narrow gap defined by a friction guide pin provided upright in the vicinity of the tape discharge gate and an elastic plate maintained in pressure-contact with the friction guide pin, thence via guide pins, and through an opening provided in the cassette body. The magnetic tape is then drawn into the cassette body with the aid of the frictional force of the magnetic tape relative to a friction member, via guide pins and a guide roller, as the tape drawing reel is rotated in the normal direction. The magnetic tape led into the cassette body, is separated from the flank portion of the tape drawing reel by means of a separation member made of synthetic resin, such as a myler film, so that the magnetic tape no longer clings to the flank portion of the reel.
Generally in the tape cassette of the tape, a reverse rotation check lever for preventing the drawing reel from rotating in a reverse direction is rotatably mounted on a support shaft. The reverse rotation check lever is combined with the separation member. A strip of tape guide member is attached to the rib of the cassette body, in a manner that the end of the tape guide member softly presses the free end of the separation member against the flank of the tape drawing reel.
When the tape drawing reel is rotated in a reverse direction, the separation member is pulled toward the flank portion of the reel by the frictional force of the separation member relative to the frictional member, whereas the reverse rotation check lever is pivotally moved about the shaft in a direction to be pressed on the flank portion of the reel. The bent end portion of the reverse rotation check lever is brought into engagement with the friction member, thereby impeding the reverse rotation of the drawing reel.
In the tape cassette, the magnetic tape pulled out of the tape housing is biased to one direction under the resiliency of the elastic strip member adapted to pressure-contact the frictional guide pin. Owing to an adequate frictional resistance is produced between the smoothing member provided at the end of the elastic strip and the magnetic tape, the magnetic tape is thus led out to the exterior in a constant tension. In this connection, the tape discharge gate must be comparatively narrow, so as to prevent the passing therethrough, of two or more runs of tape contained in a meandering fashion in the tape housing at a time. The permissible gap is, for example, on the order of 0.5 mm at the utmost, from the viewpoint of accuracy and ease of assembly.
With the conventional tape cassette of the tape, there has been encountered a problem that two or more runs of magnetic tape contained in a meandering fashion in the tape housing are liable to cling to each other under the electrostatic action, with a likelihood of being carried into the tape discharge gate. As a result, the magnetic surface of the magnetic tape is broken or two or more runs of magnetic tape clung to each other can not pass through the tape discharge gate in the worst case. Because of a difference between the frictional resistance of the magnetic tape relative to the friction guide pin and the frictional resistance of the magnetic tape surface relative to the smoothing members, the magnetic tape and the resilient strip member are liable to vibrate. The unstable travelling of the magnetic tape, result, impairing the quality of a reproduced image. Further, through the cyclical use of the tape, dust is stuck to the peripheral surface of the friction member secured to the flank portion of the tape drawing reel, or a magnetic powder falls off the magnetic layer of the magnetic tape, to be stuck to the peripheral surface of the friction member. The frictional force between the friction member and the separation member is thus impaired, with the failure to operate the reverse rotation check lever, in case of rotation in a reverse direction, of the tape drawing reel. When the endless tape cassette is removed from the video tape recorder body, the tape drawing reel is displaced from the support shaft to a portion remote therefrom, and the pressure-contact force of the separation member relative to the friction member is reduced to the lowest. In the event that the tape drawing reel is accidentally rotated in a reverse direction under such situation, rotation in the reverse direction, of the tape drawing reel can not be stopped because of the lowered frictional force between the separation member and the friction member. Unless the reverse rotation check lever is operated in the usual manner, the magnetic tape undesirably gets into the interstices between the friction member and the separation member when the tape drawing reel is rotated in a reversed direction. The magnetic tape would be broken, and in the worst case, the magnetic tape, and hence the tape cassette itself become futile.
The above-described inconveniences can be overcome by forming the separation member of a material having a large coefficient of elasticity and by strongly pressing the separation member against the friction member of the tape drawing reel. This arrangement is effective to prevent rotation in the reverse direction, of the tape drawing reel, but attended with another drawback. If the separation member is strongly pressed against the outer peripheral surface of the friction member, the pressure-contact force of the separation member acts as a braking force (a load torque) against the reel driving froce. Because of such a braking force, rotation in the normal direction, of the tape drawing reel becomes irregular when the magnetic tape is led into the cassette body, and the rotating speed of the reel becomes slow, leading to the slackening of the magnetic tape. The automatic stopping device in the video tape recorder body, in such a case, is operated, to stop the magnetic tape.